Learning the art of indexing your rear derailleur gives you crisp, smooth and efficient gear changes with reduced rattling and clanking.
Our friends at Bicycle Maintenance Guide have put together some tutorial videos and a step-by-step guide to show us how it's done. You can find tips for other mechanicals in our Spotlight on essential bike maintenance and the repair skills you need for bikepacking and cycle touring.
Check the position of the B-screw. The B-screw is the screw which sits against the flat which is on the rear hanger.
Adjusting the B-screw alters the position in which the jockey wheel on the derailleur sits beneath the sprocket of the cassette. The gap between the two wants to be around 1cm when in the easiest gear on the cassette.
Check the high and low limit positions of the derailleur are in the correct positions.
To check the high limit position, change the shifter in to the bottom gear on the cassette and check the position of the derailleur and make sure the chain is running smoothly in that gear. If it is not, this high limit position can be altered by adjusting the high limit screw. By screwing the H-screw anti-clockwise the limit position of the derailleur will move down the cassette towards the frame. Turning the H-screw clockwise causes the limit position of the derailleur to move up to the cassette towards the spokes.
To check the low limit position of the derailleur, change the shifter into the second from top gear, and then by pulling on the gear cable which is along the frame check that the derailleur indexes into the easiest gear on the cassette without struggling to change or indexing too far and hitting the spokes.
If the limit position is incorrect and requires adjusting this can be done using the L-screw. By turning the L-screw anti-clockwise the limit position of the derailleur will move to be further up the cassette towards the spokes. By turning the L-screw clockwise the limit position will move away from the spokes.
With the limit positions now set it’s time to tune the gears. Start with the chain on the big chain ring on the chainset and the smallest gear on the cassette. I
Index/change up one gear on the gear lever and look to see how the gear changes on the cassette.
If the chain doesn’t change up on the next sprocket of the cassette, but the chain does move slightly, the cable tension needs to be increased and this can be done by using the barrel adjustors.
The barrel adjustor on the rear derailleur should be rotated anti-clockwise, this tensions the cable which moves the derailleur slightly up the cassette causing the chain to change on the next sprocket on the cassette.
Carry on running up and down the cassette and if the chain doesn’t change sprocket correctly, adjust the barrel adjustor further until the gear change is smooth and the chain runs over that sprocket in a smooth manner.
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This repair has been carried out on a component from a popular brand. If you are using a different component please refer to the manufacturers manual to ensure specific details of the component/task are known. The principles and general skills of the task can be transferred but maybe not the exact details.